Monthly Archives: April 2017

The word “planet” comes from the Greek work “planan” which means to wander. Early star gazers noticed that some bright stars moved with respect to other fixed stars. Those bright stars are our closest planets: Mercury, Venus, Mars, Jupiter and Saturn. Comets also move a fair bit across the sky, but the origin of the word has more to do about stars “with long hair” than it’s traveling behavior.

Last weekend I managed to photograph comet 41P//Tuttle–Giacobini–Kresák, and I identified in my blog that it’s movement was visible frame to frame. Well I’ve finally gotten around to create a small animation of that movement. For those wondering what’s the comet’s velocity, it’s currently travelling at 37.4 km/s.

Animation of comet 41P/Tuttle–Giacobini–Kresák (41 minutes)

The above is composed of 32 frames, each a 1 minute exposure spanning a time of 41 minutes. You are probably thinking “it should be 32 minutes, not 41!”. That is because I have a delay between each frame to allow the camera to send the photo to the computer. Hence between the first and last frame, 41 minutes have elapsed.

Like this:

On April 19th a considerable sized asteroid will pass about 4.6 lunar distances (1.8 million km) from Earth. While there is no chance of it impacting our planet, this 650m asteroid was only discovered three years ago, and it will be the closest encounter of a large asteroid since asteroid Toutatis in September 2004. The next predicted fly-by of a large asteroid is 2027 with 800m wide 1990 AN10.

The expected magnitude could reach up to 11 during the close approach, hence a decent sized scope will be required, and due to the rapid movement may be hard to locate and track.

And as a bonus, comet PanSTARRS (C/2015 ER61) will also make its closest approach to Earth on the 19th, but 10 times farther away as the asteroid. I should be visible with small telescopes or binoculars in the constellation Aquarius in the dawn sky.

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Periodic comet 41P/Tuttle-Giacobini-Kresak is currently a magnitude 8 object for telescopes and unlike many other current bright comets like C/2015 ER61 (PANSTARRS) and C/2017 E4 (Lovejoy) it is visible for a good portion of the night while the other two are only visible in the morning twilight for those like me in the northern hemisphere.

On April 13th comet 41P was in the constellation Drago, which is where I managed to photograph it.

Comet 41P/Tuttle-Giacobini-Kresak (13-Apr-2017) – Benoit Guertin

Not much of a tail on this comet, and I’ve checked other photos taken with larger scopes and the result is also just a coma around the nucleus.

Because it is passing near Earth, its movement in the sky is quite noticeable frame-to-frame in the captured images. For the registration and stacking with comets, this is done by alignment on the comet and not the stars, hence the star trails in the above image. I performed another stacking, this time using the stars to align, and the comet’s movement becomes obvious. The displacement measures 2.6 arc-minutes in the 41 minutes that elapsed between first to last exposure.

My setup was less than ideal, as the constellation was only visible from the front of my house. Yes that is a lovely street-light shining right across the street. Luckily the telescope was pointing a little to the right, and a rolled piece of cardboard help act as an dew-shield extension to block the glare. But on the good side I had a nice solid concrete surface and got a very good polar alignment with 1 minutes exposures giving me nice round stars. Hmmm, might explore this setup a little more often…

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Started processing some of the images taken on April 8th, the only evening with a clear night. I spend a good hour in the near freezing air to capture Jupiter with various settings. The one below was taken with a 2X barlow and a simple webcam. This is a mosaic of two frames as not all moons fit into the rather narrow 640×480 CCD sensor. Unfortunately the fourth moon, Callisto, is just out of the frame to the right.

Took 40 seconds of video at 20 images/sec which produced a 351MB AVI file. The video is then analysed, registered and stacked with Registax. Color saturation and light levels where then adjusted in GIMP.

I also took many more video with a 3x barlow, but getting the focus right was a challenge. And I’m afraid the end result is just a “bigger” Jupiter, no additional details. I will need a few nights to process those and see which one turned out well. I will also try using the drizzle algorithm on the image above to see if I can get a larger and better image.

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This weekend is the best time to see Jupiter of all 2017, because the planet is at opposition, meaning it is exactly opposite to the Sun and the Earth-Jupiter separation is also at its closest.

The photo below was taken during the September 2010 event and I happened to fall upon a fantastic low turbulence window in the atmosphere. Look closely and you’ll see the shadow of one of those moons on the Jupiter’s surface.

Jupiter – Benoit Guertin

Photos of Jupiter with the moons are a little tricky. Capturing the smaller moons require more exposure or gain, but at the risk of over-exposing the planet and turning Jupiter with those wonderful cloud bands into nothing more than a white sphere. It is always better to take a series of images or videos with different settings and review them at a later time on the computer. Some information on planetary imaging and processing is provided in my blog on imaging with a webcam.

Planetary imaging is all about controlling turbulence. Air turbulence whether within the optics, telescope, near the ground or high atmosphere will give you a blurry view. Hence some simple tips are:

Allow your equipment to cool down a few minutes such that the equipment temperature can stabilize and match the outdoors.

Past midnight is better as this allows time for the ground to cool especially after a sunny afternoon, reducing convective currents.

Wait until Jupiter is high in the sky, that way there is less atmosphere between you and Jupiter. By looking straight up, you will be looking through a smaller “air column”.

A good time will be on April 10th when the Moon will next to Jupiter. See the sky chart below showing the southern part of the sky at 10pm EDT. The planet will track west as the night advances.

Welcome to a journey into our Universe with Dr Dave, amateur astronomer and astrophotographer for over 40 years. Astro-imaging, image processing, space science, solar astronomy and public outreach are some of the stops in this journey!